1. Field
The present invention relates to a drainage system for transferring waste water gathered from fixtures of various types disposed at different heights or levels, mainly in a vertical direction to a drain pipe disposed in a lower position. The drainage system according to the present invention is particularly suitable for installation in a high-rise building.
2. Prior Art
A drainage system for conducting waste water from such fixtures as toilets and bathrooms installed in a multi-story building to the underground sewer main or any other drainage equipment is generally provided with an approximately vertically extending main pipe or stack which is connected at the lower end to the public sewerage, and also provided with generally horizontally extending branch pipes for conducting waste water from fixtures on each floor to the stack. The upper end of the stack is open to the atmosphere. When waste water from a certain branch pipe flows down through the stack, the pressure in the stack is low in an upper position of the waste water and high in a lower position. The inflow timing and amount of waste water from each branch pipe into the stack are usually very irregular, so the pressure developed irregularly in the stack may impede a smooth flow of waste water. In some cases, a positive or negative pressure is so large as to destroy the waste trap attached to the equipment. The longer the stack in the vertical direction, the more remarkable this tendency, so in the drainage system for a high-rise building employing a very long stack there usually is provided a vent means for preventing variation in the intra-stack pressure separately from the drain pipe.
FIG. 1 shows a known drainage system having such vent means. A stack 1 extending vertically through the floor of each story is connected at the lower end thereof to a horizontal pipe 2 which is connected to a public sewerage 10, and the stack, at the upper end thereof, is connected to a vent pipe 3. The other end of the vent pipe 3 is open to the atmosphere. Numeral 4 denotes a drain branch disposed along each floor. Each branch is connected to the stack 1 through a connector 5 to conduct waste water from a fixture 6 such as a toilet bowl to the stack 1. Numeral 7 denotes a main vent disposed near the stack 1 approximately in parallel therewith. The main vent 7 is connected at both ends thereof to both ends of the stack 1 and further connected to the stack 1 in arbitrary longitudinal positions through connecting vent pipes 8. Further, branch vents 9 are provided if necessary. The branch vents 9 are connected to the main vent 7 in arbitrary positions through the drain branches 4.
Waste water from any of the fixtures 6 flows into the stack 1 through the drain branch 4 to which the fixture is connected and further through the connector 5, then flows down through the stack and enters the sewer pipe through the horizontal pipe 2. During this period, a pressure variation which occurs in the stack 1 or which in some case may occur also within the horizontal pipe 2, is absorbed by the air introduced from or discharged to the main vent 7, whereby smooth drainage is ensured.
The greatest problem of such known drainage system resides in the complexity of the piping structure including the main vent 7 which must be provided separately from the stack 1 and the connecting vent pipes 8 which connect the main vent 7 to the stack 1. Such a complicated piping structure is disadvantageous in point of the working cost and the construction period required. And an accident such as water leakage is very likely to occur. Another drawback of the known drainage system which should not be disregarded is that there occurs turbulence of flow at the portions where waste water changes its flowing direction largely, that is at the connections between the drain branches 4 and the stack 1 and at the connection between the stack 1 and the horizontal pipe 2, the said turbulence not only enlarging the pressure variation but also causing noise, with the result that the performance limit of the entire system remains low.